1. Field of the invention
Fiber reinforced composite materials can be used to manufacture components by processes which include reaction injection molding, compression molding, pultrusion or filament winding. Advantageously, components so manufactured have better or comparable physical properties than components made of conventional compositions while being substantially lighter in weight and also corrosion resistant. In addition, less energy is generally required to manufacture a fiber reinforced composite component than is necessary to manufacture the functionally equivalent component made of conventional materials, such as steel. Still further, this replacement component is often smaller in size than the conventional component, a relevant consideration for manufacturing operations wherein components are shipped. These features of resin-fiber components would obviously be of great importance in a variety of applications, one particularly of interest being the manufacture of car components, where these composite materials could be fabricated into, for example, leaf springs and body support members.
Leaf springs made from the resin-fiber composites of the subject invention possess at least 25% greater interlaminar shear strength and more than 2 times greater impact total energy (Ft-lbs) than those made of commercially available vinyl ester material. Additionally, these springs weigh 40% less than conventional springs. It appears that leaf springs made of the binder-fiber composite, of this invention, in view of their physical properties, also would be suitable for use in trucks.
The resin of this invention has been found to be an excellent binder for chopped, woven, or continuous fiber (e.g., graphite, glass and Kevlar) reinforced composites. It exhibits good wetting of the fibers, fast gelling and rapid cure. In addition, the binder of this invention, when reinforced with fiber, possesses excellent physical properties, including increased interlaminar shear strength, when compared to composites made with currently available vinyl ester or polyester binders. Furthermore, although one advantage of the subject binder is its potential for extremely rapid cure, the addition of a cure inhibitor prior to the addition of the initiator, for ambient temperature cure, can prolong gel time and retard the cure rate. Thus, by selecting the particular cure initiator or inhibitor and initiator, cure time can be tailored to meet the specific cure conditions preferred for the binder-fiber composites. Additionally, the low viscosity of the subject binder composition contributes to its advantageous suitability for a variety of uses and processes.
2. Description of the Relevant Art
U.S. Pat. No. 3,971,834 to Uzelmeier et al teaches reacting a polyepoxide with both a secondary amine and an ethylenically unsaturated conjugated carboxylic acid to form a photocurable acrylate resin coating exhibiting improved adhesion to metals. U.S. Pat. No. 4,253,918 to Traenekner et al teaches reacting polyepoxides with both (meth) acrylic acid and a nitrogen containing compound to form air drying coating compositions, preferably from use on paper and cardboard.
As in this application, which claims the reaction of a polyepoxide with a secondary amino alcohol, these patents teach that a polyepoxide may be reacted with a secondary amino alcohol. However, while both of these patents teach reacting only a portion of the available epoxide groups of the polyepoxide with the amino compound, the subject application claims reacting the epoxy and amino groups in about a 1:0.95-1.2 equivalent ratio, so as to react substantially all of the epoxide groups of the polyepoxide with the amine. In these patents, the unreacted epoxide groups of the polyepoxide are reacted with an unsaturated acid. However, in the case of the subject invention, wherein substantially all of the epoxide groups have been reacted, the hydroxyl moiety of the epoxy-amino alcohol adduct is then reacted with a vinyl containing compound through a hydroxy reactive functionality of the vinyl compound, (e.g., the epoxide of glycidyl methacrylate). Thus in these patents, the vinyl unsaturation is added at one end of the polyepoxide and the amine alcohol, when used, is added at the opposite end of the polyepoxide, while in the subject application, the amino alcohol and the vinyl unsaturation are added, in stepwise fashion, at each end of the polyepoxide.
An object of this invention is to prepare resin-binder compositions, which cure more rapidly than conventional compositions, and which in combination with reinforcing fiber show improved interlaminar shear strength. It has now been found that incorporation of the tertiary amine into the epoxy backbone in combination with the terminal vinyl unsaturation added to the adduct gives a composition with these highly desirable characteristics. In particular, it appears that the incorporated tertiary amine serves as a catalyst for the addition of the vinyl unsaturation as well as for subsequent crosslinking of the prepolymer vinyl group with vinyl groups of the diluent during cure.